The Portuguese winger was forced off late in the first half of United's 2-2 draw with Chelsea at Old Trafford yesterday afternoon.
Despite the fact the 26-year-old appeared to be clutching his hamstring in pain as he left the pitch, Ferguson has described the injury as not "too serious".
"Nani got a little hamstring injury. I don't think it's too serious but nonetheless he had to come off," the Scot told MUTV. "That was a blow to us because Nani was playing very well at the time."
A succession of different injuries have limited Nani to just 18 appearances this season.